1. Field of the Invention
The present invention relates to driving method and apparatus to a light emitting device.
2. Description of Background Information
Display units using a light emitting device are widely used in electronic devices in recent times. In some cases, a desired display is achieved by changing the luminance of the light emitting device.
Conventionally, the luminance of a light emitting device is changed by using a plurality of power supplies generating different outputs. Among the plurality of outputs from those power supplies, outputs which can be used to produce desired luminance are selected by using switches and resulting outputs are summed to drive a light emitting device.
As described above, in conventional cases, to change the luminance of a light emitting device two or more power supplies are prepared and output values of the power supplies by which a target luminance can be obtained are selectively transmitted to drive the light emitting device.
Therefore, such driving apparatuses are complicated and expensive because of the requirement of a plurality of power supplies. Also, such apparatuses use a number of control signal lines and much time is needed to adjust the output values of the power supplies to specified levels.